Powerline communications (PLC) include systems for communicating data over the same medium (i.e., a wire or conductor) that is also used to transmit electric power to residences, buildings, and other premises. Once deployed, PLC systems may enable a wide array of applications, including, for example, automatic meter reading and load control (i.e., utility-type applications), automotive uses (e.g., charging electric cars), home automation (e.g., controlling appliances, lights, etc.), and/or computer networking (e.g., Internet access), to name only a few.
Current and next generation narrow band PLC are multi-carrier based, such as orthogonal frequency division multiplexing (OFDM)-based (as opposed to frequency shift keying (FSK)-based) in order to get higher network throughput. OFDM uses multiple orthogonal subcarriers to transmit data over frequency selective channels.
FIG. 1 is a system model depiction of a PLC network 100 for local utility PLC communications, configured for U.S. deployment: LV nodes 105 include meters having modems 110 which during uplink communications transmit usage and load information (“data”) using the low voltage (LV) access network portion 125a of powerline 125 through the transformer 120 over the MV network portion 125b of powerline 125 to one or more medium voltage (MV) routers (also called switch nodes) 130. In turn, each MV router 130 forwards this data to the data concentrator (or base station) 140, which sends the data to the utility company 160 over a telecommunication backbone 150. During downlink communications (router 130 to LV node 105) the direction of communications is reversed relative to uplink communications.
Multi-Tone Mask (MTM) mode (or “tone masking”) refers to the use of multiple tone-masks/sub-bands to enable nodes in the network to each select individual tones within the band utilized by the network for network communications including PLC networks such as those based on the IEEE P1901.2. MTM mode for tones allows avoidance of parts of the network spectrum occupied by high levels of external noise. MTM mode also allows co-existence with incumbent communication technologies (such IEEE P1901.2 with IEC 61334, IEEE P1901 and ITU G.hn) that might be sharing the PLC channel.
When operating in MTM mode, only one/set of TMs may be optimal (typically the lowest noise) for each particular unidirectional/bidirectional link. After each node (device) performs an initial tone mask scanning, the nodes determine which tones are optimal for their UL communications (node to router) and for their DL communications (router to node). The UL and DL may have a different optimal TM/sub-band, and thus may be operated using different tones. Thus, while operating in the MTM mode where each node uses a different UL/DL TM for communications, the router 130 must support all the network nodes served.